CN1341576A - Preparation of high-purity titanium biboride ceramic micropowder by using self-spreading high-temp. reduction synthesis process - Google Patents

Abstract

The self-propagating high-temperature reduction synthesis method to prepare high-purity titanium diboride ceramic powder is to use active metal reducing agent and cheap oxide raw materials to spontaneously synthesize high-purity _TiB2 ceramic powder through strong exothermic chemical reaction. In the present invention, TiO ₂ , B ₂ O ₃ and metal Mg powder are uniformly mixed and molded, then placed in argon-protected self-propagating high-temperature synthesis device at normal temperature and pressure, ignited and burned, and the combustion products are crushed and pickled. Finally, high-purity _TiB2 ceramic micropowder is obtained. The invention has the advantages of higher purity, finer crystal grains, simple process, less energy consumption and less time consumption than traditional carbothermal reduction _TiB2 ceramic powder. Compared with SHS elemental synthesis of _TiB2 ceramic powder, the manufacturing cost is low.

Description

Preparation of high-purity titanium diboride ceramic powder by self-propagating high-temperature reduction synthesis

Technical field

The invention relates to a refractory compound and a solid phase synthesis method thereof.

Background technique

Titanium diboride ceramic powder is an important new type of engineering ceramic raw material. Its important physical and chemical properties include: high melting point (>3000°C), high hardness (>30GPa), high chemical stability, and high thermal conductivity. (120W/mK), high modulus (>570GPa), excellent electrical conductivity. Mainly used in: hard tool materials, composite material additives, new heating elements (>1800°C), high-temperature inert electrodes (>1200°C), high-temperature wear-resistant electrodes, high-temperature corrosion-resistant electrodes, high-strength lead frames for large-scale integrated circuits materials etc. However, the high price of high-purity _TiB2 raw materials limits the large-scale development and application of such materials. The traditional synthesis process of titanium diboride ceramic powder is: put the mixture of titanium or titanium dioxide, boron oxide or boron carbide and carbon in a vacuum graphite tube furnace, and then heat it to about 1800°C for carbonization and reduction. The reduction time is generally 1 ~12 hours. The main disadvantages of this method are: complex production equipment, high reaction temperature, long time, huge energy consumption, coarse grains of titanium diboride obtained, low boron content, and poor product purity. Chinese patent CN105533A reports a carbon thermal reduction synthesis method of titanium diboride ceramic powder based on activated carbon as a reducing agent, ammonium pentaborate as a boron source and titanium dioxide as a titanium source. The time is long and the particle size of the product is coarse (about 10 μm).

Self-propagating high-temperature synthesis technology (SHS technology for short) is a new material processing technology that uses the heat released by chemical reactions to make combustion reactions proceed spontaneously to obtain combustion products with specified components and structures. Compared with many traditional material preparation technologies, SHS technology has the following advantages: simple process, short process cycle; low energy consumption, obvious energy saving effect; high purity of synthetic products; high sintering activity can be obtained due to the large temperature gradient experienced during the synthesis process synthetic products. Titanium diboride ceramic powder is one of the earliest materials synthesized by SHS technology. Z.A.Munir reported the element synthesis method of titanium diboride powder in 1988. It is based on high-purity boron powder and titanium powder or titanium hydride powder. Raw materials are prepared. The powder synthesized by this process has high purity, but the particle size of the powder is large and some of them form hard aggregates; in addition, because the raw materials used are simple elements, the manufacturing cost is high and industrial production cannot be achieved.

Contents of the invention

The technical problem to be solved by the present invention is to propose a method for preparing titanium diboride ceramic micropowder by a self-propagating high-temperature reduction synthesis method based on oxide raw materials in view of the defects in the prior art.

The technical solution adopted by the present invention to solve the technical problem is: uniformly mix TiO ₂ , B ₂ O ₃ and Mg powders and mold them into a self-propagating high-temperature synthesis device protected by argon under normal temperature and pressure (National Utility Model Patent: ZL93216816.7), ignition and combustion; the combustion product is crushed and pickled to obtain high-purity TiB ₂ ceramic powder.

TiO ₂ , B ₂ O ₃ powder and metal Mg powder are the main reaction materials, according to the reaction formula , forming products whose basic components are _TiB2 and MgO, Q is the reaction exotherm. Because in the above reaction system, the heat release of the reduction reaction between TiO ₂ , B ₂ O ₃ and metal Mg is much smaller than the heat release of the synthesis of Ti and B elements, the combustion temperature is lower than 2200°C and the reaction time is within a few minutes (generally 1 to 2 minutes) to complete, the product crystal grains formed in this way are fine and do not agglomerate, and are easy to break.

Concrete realization process of the present invention is described in detail as follows:

1. Uniformly mix TiO ₂ , B ₂ O ₃ and Mg powders and mold them, place them in argon-protected self-propagating high-temperature synthesis device (national utility model patent: ZL93216816.7) at room temperature and pressure, ignite and burn, Combustion products are obtained.

Among them, the particle size of TiO ₂ powder should be less than 80 μm, that of B ₂ O ₃ powder should be less than 120 μm, and that of Mg powder should be less than 200 μm.

The composition of TiO ₂ , B ₂ O ₃ , and Mg powder raw materials for self-propagating high-temperature reduction synthesis is as follows: TiO ₂ is 27-29 wt%, B ₂ O ₃ is 26-28 wt%, and Mg is 43-47 wt%.

2. The purification and separation of TiB ₂ ceramic micropowder can be realized according to the following process: the combustion product is crushed by a ball mill and sieved to obtain a powder with a particle size of less than 0.5mm; Pickling in 1 hydrochloric acid or sulfuric acid at a temperature of 20-80°C for 1-10 hours, and the obtained product is filtered and dried to obtain high-purity titanium diboride ceramic powder.

High-purity _TiB2 ceramic micropowder is synthesized by self-propagating high-temperature reduction synthesis (SHRS) technology combined with chemical purification, and its composition is: Ti67-69wt%, B29-32wt%, O≤0.75wt%, N≤0.1wt%, Mg≤ 0.15wt%, the average particle size is 5μm.

The present invention has the advantages of higher purity, smaller crystal grains, simple process, less energy and time consumption than traditional carbothermally reduced _TiB2 ceramic powders; at the same time, the manufacturing cost is 20% compared with SHS elemental synthesis of _TiB2 ceramic powders About, and the grain size is 1/10 to 1/4.

Specific implementation plan

Example 1: 27 grams of TiO ₂ powder (≤80 μm), 26 grams of B ₂ O ₃ powder (≤120 μm), and 47 grams of Mg powder (≤200 μm) were thoroughly mixed. The mixed sample is pressed into a block blank, put into a self-propagating high-temperature synthesis reactor, and under the protection of argon gas at normal temperature and pressure, the surface of the sample is ignited with a tungsten wire or an electric arc. The combustion wave spreads rapidly. At this time, the combustion temperature of the sample is 1800-2000°C, and the combustion reaction is completed within 1-2 minutes. After the sample was completely cooled, it was placed in a ball mill for ball milling for 2 hours. The obtained powder was put into a reaction kettle, 10 liters of hydrochloric acid with a concentration of 1 mol/l was added and stirred continuously, acid washed at 50° C. for 4 hours, filtered and dried. The composition of the obtained micropowder is: Ti68.2wt%, B30.1wt%, O0.5wt%, N0.1wt%, Mg0.1wt%, and the average particle diameter is 4.7 μm.

Example 2: 29 grams of TiO ₂ powder (≤80 μm), 26 grams of B ₂ O ₃ powder (≤120 μm), and 45 grams of Mg powder (≤200 μm) were thoroughly mixed. The mixed sample is pressed into a block blank, put into a self-propagating high-temperature synthesis reactor, and under the protection of argon gas at normal temperature and pressure, the surface of the sample is ignited with a tungsten wire or an electric arc. The combustion wave spreads rapidly. At this time, the combustion temperature of the sample is 2000-2200°C, and the combustion reaction is completed within 1-2 minutes. After the sample was completely cooled, it was placed in a ball mill for ball milling for 2 hours. The obtained powder was put into a reaction kettle, 20 liters of sulfuric acid with a concentration of 0.5 mol/l was added and stirred continuously, acid washed at 50° C. for 6 hours, filtered and dried. The composition of the obtained micropowder is: Ti68.8wt%, B30.35wt%, O0.7wt%, N0.1wt%, Mg0.05wt%, and the average particle diameter is 5.8 μm.

Example 3: 29 grams of TiO ₂ powder (≤80 μm), 28 grams of B ₂ O ₃ powder (≤1200 μm), and 43 grams of Mg powder (≤200 μm) were thoroughly mixed. The mixed sample is pressed into a block blank, put into a self-propagating high-temperature synthesis reactor, and under the protection of argon gas at normal temperature and pressure, the surface of the sample is ignited with a tungsten wire or an electric arc. The combustion wave spreads rapidly. At this time, the combustion temperature of the sample is 1700-1900°C, and the combustion reaction is completed within 1-2 minutes. After the sample was completely cooled, it was placed in a ball mill for ball milling for 2 hours. The obtained powder was put into a reaction kettle, 10 liters of hydrochloric acid with a concentration of 1 mol/l was added and stirred continuously, acid washed at 50° C. for 4 hours, filtered and dried. The composition of the obtained micropowder is: Ti67.87wt%, B31.3wt%, O0.6wt%, N0.1wt%, Mg0.13wt%, and the average particle diameter is 4.1 μ m.

Claims (1)

1. The method for preparing high-purity titanium diboride ceramic micropowder by using self-propagating high-temperature reduction synthesis method is characterized by that TiO is added₂、B₂O₃Uniformly mixing Mg powder, carrying out compression molding, putting the mixture in a self-propagating high-temperature synthesis device under the protection of argon at normal temperature and normal pressure, and igniting and burning the mixture to obtain a product mixture;

wherein the TiO is₂The particle size of the powder is less than 80 mu m, B₂O₃The particle size of the powder is less than 120 mu m, and the particle size of the Mg powder is less than 200 mu m;

crushing the product mixture, pickling in hydrochloric acid or sulfuric acid with the concentration of 0.5-2.0 mol/l at the temperature of 20-80 ℃ for 1-10 hours, and filtering and drying the obtained product to obtain high-purity titanium diboride ceramic micropowder;

the micro powder comprises the following components: 78-69 wt% of Ti67, 32-32 wt% of B29, less than or equal to 0.75 wt% of O, less than or equal to 0.1 wt% of N, less than or equal to 0.15 wt% of Mg, and 5 mu m of average grain diameter.